FIGS. 1 and 2 illustrate a prior art Fresnel lens 10. The prior art Fresnel lens 10 includes a transparent lens portion 12 and a redirecting lens portion 14. The transparent lens portion 12 is a substantially transparent disc or plate having a front side 16 and a rear side 18. The redirecting lens portion 14 extends from the rear side 18 of the transparent lens portion 12. The redirecting lens portion 14 includes a plurality of sawtooth-shaped protrusions 20 extending from the transparent lens portion 12. Each protrusion 20 includes a non-refracting surface 22 and a refracting surface 24. As is well known to those skilled in the art, the non-refracting surfaces 22 of the protrusions 20 are configured to be substantially parallel to rays of light which enter the lens 10 such that the light will not refract off of the non-refracting surfaces 22. If the rays of light entering the front side 16 of the transparent lens portion 12 of the prior art Fresnel lens 10 are parallel to each other, the non-refracting surfaces 22 can be parallel to each other and perpendicular to the front side 16 of the transparent lens portion 12. The light will then refract off of the refracting surfaces 24 to alter the direction of the light. Alternatively, light can enter the lens 10 through the redirecting lens portion 14 and be redirected by the refracting surfaces 24. The non-refracting surfaces 22 can be parallel to the light entering the lens 10 so as to minimize refraction of the light or the refracting surfaces 24 can be configured to redirect light entering the lens 10 away from the non-refracting surfaces 22. The refracting surfaces 24 can be parallel to each other to redirect the angle of all of the light rays at the same angle or can be at slightly different angles to focus the light travelling through the prior art Fresnel lens 10 at a single area.
FIGS. 3 and 4 illustrate a second embodiment of a prior art Fresnel lens 10a, wherein the protrusions 20a form a plurality of concentric circles with a normal convex lens 26 in a center of the lens 10a. Prior art Fresnel lenses can take other forms and have other configurations as is well known to those skilled in the art, wherein such lenses each have a plurality of projections, with each projection having a non-refracting surface and a refracting surface.